


Dance Upon the Mountains Like a Flame

by wankernumber9



Series: Harmonices Mundi [4]
Category: Doctor Who (2005)
Genre: F/F, Science Fiction, Slow burn Thasmin
Language: English
Status: Completed
Published: 2019-02-13
Updated: 2019-03-22
Packaged: 2019-10-27 07:26:55
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 16,570
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17762423
Author URL: https://archiveofourown.org/users/wankernumber9/pseuds/wankernumber9
Summary: After the incident on the space station, Yaz visits her family, the Doctor ponders fleeing, Ryan and Graham tease them both, and the mystery gets deeper.





	1. Home to Roost

**Author's Note:**

> _"Faeries, come take me out of this dull world,_  
>  _For I would ride with you upon the wind,_  
>  _Run on the top of the dishevelled tide,_  
>  _And dance upon the mountains like a flame."_ \- William Butler Yeats

It was early, relatively speaking.

Yaz and the Doctor were in the galley, enjoying breakfast together ahead of the boys' inevitable grumbling arrival. They sat across from each other as the Doctor sliced a nectarine into increasingly complex shapes, showed off her handiwork to Yaz, then popped the slices into her mouth. Yaz propped her chin on her hand, watching her friend while she munched on toast with jam.

Neither said much, instead simply enjoying the shared moment of quiet before the day's adventure began. Yaz eventually found herself grinning, which of course the Doctor noticed, and she smiled back before bashfully returning her attention to artful fruit deconstruction. It all felt just a bit... flirty.

Yaz finished her toast and set aside her plate, then leaned in. "Doctor," she began.

The Doctor cocked her head and waited, knowing that tone of voice. Yaz was about to ask for a favor. It occurred to her that she _loved_ that she knew that, and she sat up a little straighter in anticipation.

"I was wondering," Yaz continued.

Ryan shambled into the galley, rolling his eyes as he set course for the coffee. "Whatever it is, you know she'll say yes," he muttered.

"Oi!" both women complained at once.

He held his hands out in defense. "She's about to ask you for something," he said, pointing at Yaz. "And you _always_ say yes!" he concluded, pointing to the Doctor. "'Doctor, can we go see my grandmother?' 'Doctor, can we go to Pluto?' 'Doctor, can we go shopping in the largest mall in the universe?'"

"Oh no, not again," Graham grumbled as he wandered in on the tail end of Ryan's impression. "My feet still hurt from last time."

"Graham, I told you, the inter-dimensional store transporters would have sorted that," the Doctor said.

"By phasing my body into an adjacent plane of existence that _happens_ to have housewares and men's belts?"

The Doctor chewed on a chunk of nectarine and nodded, as if it were the most commonplace suggestion he'd ever made.

"No, thank you. I'd rather my feet hurt. At least then I know they're still attached," Graham decided. "And anyway, Yaz, can't we go someplace else?"

"I didn't _say_ I wanted to go back there," Yaz said, exasperated.

"Oh, I just figured..." Graham shrugged, gesturing between her and the Doctor. "Could you ask her if we could go to a beach planet? Some place with fruity drinks with those little umbrellas?"

"You can ask her yourself," Yaz said. "She says yes to you lot, too."

"Not all the time," Ryan said. "Like when I wanted to go to the Neptunian Gladiator bouts..."

" _No!_ " Yaz and the Doctor exclaimed, in simultaneous objection.

"They're barbaric," Yaz argued.

"The Neptunian fights are completely overrated anyway," the Doctor added. "I'll take you to a proper one back in Rome, sometime."

"Really?!"

" _No_. They're barbaric," the Doctor said, annoyed. She reached into the fruit bowl to grab another nectarine, tossed it at him carefully, then focused again on Yaz. "Now. You were saying?"

"I was thinking I'd like to go home, to see my parents." She dropped her gaze and withdrew a little, anxious about the next request. "And maybe invite them to see the TARDIS?"

The Doctor jolted in delight. "Yaz's Mum and Dad! Brilliant! Back to Sheffield and Yaz's flat!" She turned to Ryan and Graham. "I can drop you boys off someplace for those fruity drinks, if you like?"

"Oh, no. I need to see this," Ryan said, around a mouthful of nectarine.

"Me too, Doc," Graham said. "Moral support and the like." He lifted a cup of coffee in a toast of sorts to Yaz, who was already definitely regretting _everything_ about this particular idea.

* * *

"Hi! I'm home!" Yaz stepped into the flat, channeling her brimming anxiety into enthusiasm to see her family.

The response wasn't exactly rousing. Sonya lounged across the sofa, holding her phone over her face. She sort of waved in Yaz's general direction. At the kitchen table, Najia barely looked up from reading the paper.

"Where have you been?" Najia asked. She peered at her over the top of her reading glasses as she flipped the newspaper page.

That was a fair question. Yaz checked her phone. It was the second of January, the day after they'd defeated the Dalek scout here on Earth, late in the afternoon. The chair in Graham's front room was probably still in pieces. Where _had_ she been since then? She thought back. 

"The thirty-third century," she replied with a grin. She moved to a chair at the table and sat by her mother.

Sonya muttered something that sounded like "so weird," with a roll of her eyes so exaggerated it probably hurt.

Najia just looked Yaz over with a skeptical eye. "Surprised to see you here without your 'friend,' the Doctor."

"Oh, she's here," Yaz said, ignoring her mother's barbed tone. "Waiting outside, actually. Is Dad around?"

"He's working the evening shift," Najia answered.

That was unfortunate. For a moment Yaz considered putting off her plan, but she wasn't sure she'd ever work up the nerve again. She took a deep breath. "Do you have a minute? There's something I'd like to show you."

"You know your Nani's coming over for dinner," Najia said.

"You'll be back before then," Yaz said, and quietly hoped that was true. "It won't take long." She met her mother's serious gaze and leaned in. "Please, Mum. It's important."

Najia pulled off her glasses and studied her daughter. "What's going on?"

Yaz stood, and pulled her mother's coat off the hook by the door. "Please?"

* * *

Her mother wasn't moving quickly enough, and Yaz had to resist the urge to pull her forward, toward the TARDIS as it shimmered at her through its perception filter.

"You said the Doctor was here? Waiting outside? What is it you wanted to show me?" Najia stopped in her tracks, and grabbed hold of Yaz's hand. "You didn't go off and get married, did you?"

"What?! Mum, _no_." Yaz succumbed to impatience and tugged her along, shepherding her toward their destination.

"Because I know the world has changed, and you can make a life with whomever you please," Najia continued. "But you do _not_ get to get married without inviting your family..." She stopped, and realized she was looking at an old Police Box standing on the lawn in front of their flat. "How long has that been there?" she asked, confused.

"Not long," Yaz answered. "We just arrived."

The door popped open, and the Doctor leaned out. "Hi, Yaz's mum!"

"It's _Najia_ ," Najia corrected automatically. "Doctor? What are you doing in there?" 

"Making s'mores," the Doctor said brightly. "Want one?"

Yaz sighed. "This is what I wanted to show you," she said to her mother. "It's a spaceship, called the TARDIS."

Najia blinked, slowly. "What?"

"This is where I've been. Traveling with the Doctor, in her ship." She moved to stand by the door, and shoved her hands into her pockets. "Well, not just me. Remember Ryan Sinclair and his granddad?"

"This isn't funny, Yasmin," Najia said. She looked around. "Is there someone filming right now?"

"No, Mum, please just come inside." Yaz followed the Doctor into the TARDIS, and beckoned to her mother.

"What, with you two? In that tiny..." She peered inside, where it immediately opened into the console room. She stepped in, tentative and uncertain, with her mouth hanging open.

From the other side of the room, Ryan waved. "Hi Mrs. Khan," he called dutifully.

Graham stepped up, giving her a polite nod. "Welcome aboard. This probably all seems a bit strange..."

Najia whirled on the Doctor. "Who _are_ you?!"

"I'm the Doctor," she answered, amiably. She shoved her hands into her pockets and rocked on her heels. "And as Yaz mentioned, this is my ship."

"This is a _ship_ ," Najia repeated, untangling the many implausibilities presented at once.

The Doctor nodded. "Also a time machine," she added. She blanched at Yaz's immediate wince. "Too much information? Sorry. Trying to be helpful. Ryan got in my head."

"It was a _joke_ ," he insisted. "'Meeting the in-laws,'" he explained, in a stage whisper to Yaz, who glared pure murder back at him.

Najia reached out and put her hand on Yaz's shoulder to steady herself while she looked around.

"Anywhere you'd like to see?" the Doctor ventured. 

"I... don't know," Najia said, bewildered.

"Mum always liked Saturn," Yaz said suddenly. It was true, but it wasn't until that exact moment that she remembered a childhood trip to the observatory, and her mum lingering over the planetary prints in the gift shop.

"Oh, Saturn, brilliant! Love a good gas giant. Let's go," the Doctor declared, as she started her usual maneuvers around the console.

(If her movements were a bit less theatrical than usual, her companions had the good grace not to mention it.)

Graham sidled up to Najia and guided her carefully over to a nearby column. "You'll want to hang on. Sometimes these hops get a bit bumpy."

After minimal turbulence, they dropped out of the time vortex, drifting comfortably amongst Saturn's moons. The Doctor waited, giving Yaz an expectant look.

"Mum, you have to see this," Yaz murmured. She crossed the console room to open the doors to the stellar panorama beyond, and couldn't help but catch her breath at the sheer beauty of the golden planet.

Najia looked like she was trying not to hyperventilate as she took in the dark and dust of the remarkable rings.

"That rock is Rhea," the Doctor said, pointing to the moon evident off to port. "Saturn's fifth moon, about to be discovered... tomorrow, actually. Right now we're in December, 1672." She grinned and bounced, just a little. "Oh, and in a thousand years, they'll host positively dreadful golf tournaments there."

"So, you lost?" Ryan asked, knowingly.

"The archduke cheated," the Doctor scoffed.

Yaz was watching her mother as she clung, white-knuckled, to the open TARDIS door. "Mum?" she said.

"How is this real?" Najia whispered.

"Amazing, right?" Yaz asked. She took out her phone and snapped a picture. "I'll send that to you." She slung an arm across her mum's shoulders, basking in the wonder of the moment, so glad to finally have shared this secret.

Behind them, Ryan bumped against Graham's shoulder with a smile, similarly enjoying the bonding moment between their extended fam.

"Where else have you gone?" Najia asked after a long moment.

"Everywhere," Yaz said, casting a grin back at the Doctor.

She felt the moment her mother withdrew into herself, felt the sinking feeling in her gut as Najia turned to glare at the Doctor once more.

"Tell me, Doctor. How is my daughter supposed to go back to a normal life after this?" Najia asked. "How can the real world be good enough for her ever again?"

"I suspect it never was good enough to begin with," the Doctor answered calmly. "She's a rather extraordinary person."

Yaz considered objecting to being the subject of a conversation while she was standing right next to it, but instead was caught short by how the Doctor and her mother were studying each other, as if measuring each their respective intentions.

"I'd like to go home, now," Najia said quietly.

"Of course," the Doctor said. She flashed a brief, worried expression at Yaz and moved back to the console.

The TARDIS herself seemed mindful of her tenants' unsettled mood, and, according to Yaz's phone, deposited them back a mere twenty minutes after their original departure.

With the familiar Sheffield drizzle back in view, Najia heaved a sigh of relief, and aimed all her remaining worry for her daughter's safety back at the Doctor. "You're not human," she said.

"No," the Doctor replied.

"And you're probably not as young as you look."

"Definitely not."

"So, my daughter and her friends... I assume they're not the first strays you've dragged around the universe?"

Graham was ready to object, but the Doctor stopped him with a gesture. "No, they're not," she answered.

"What happens when they grow old? When they die? Do you just wander about and kidnap a few more humans to entertain you?"

"Mum!" Yaz snapped. "We _asked_ to be here."

"She's right," Ryan said, jumping to Yaz's defense. "We all wanted to come."

Najia fixed Ryan with an intense, curious look. "Why?"

He wasn't expecting that entirely reasonable question, and he faltered. "After my nan died, I just... didn't see the point of real life anymore, you know? Traveling with the Doctor makes that better."

Najia dipped her head, acknowledging his loss and backing off a bit. "Is that why you're here? You didn't see 'the point' of real life?" she asked her daughter, wistfully. She sighed and stepped out of the TARDIS, heading back home.

"Mum," Yaz called. She gave the Doctor an anguished look and hurried after her mother. "It's not like that, for me," she argued, as she jogged to catch up. "Ryan and Graham, they were grieving. They needed to get away. I just... needed to _go_ , somewhere."

"With _her_." Najia didn't even slow. The thudding of her heels on the wet pavement knocked out a resolute, mournful rhythm.

"Yes, with her."

Najia reached the lift, jabbed the button for their floor, and waited to ascend in silence. Yaz followed, all the way to the point where her mother hung her coat back on the hook in the family flat.

"I was never going to marry some nice Muslim man and be bored the rest of my life," Yaz said, quiet and miserable.

"You mean, like I did?" Najia countered.

Yaz sighed. "That's not what I meant," she said, before thinking better of it. "Except yes, it is! I _know_ how clever you are. I know you gave up school for your family. I know you could have done literally anything."

"I've made my choices, and I love my family. For some of us, that's enough."

"That was never gonna be enough for me," Yaz declared. "And don't blame the Doctor for that, Mum. She's not the problem. She's not even the solution. She's my _friend_. She makes me more than I am on my own."

"What on earth does _that_ mean?" Najia asked. "Do you even know?"

Yaz's train of thought abruptly derailed. What _did_ that mean? She felt her cheeks heat with sudden embarrassment at an admission she hadn't meant to make.

"Let her go, Najia," came a voice from the kitchen table. Umbreen sat, previously unnoticed, at the kitchen table, with a cup of tea.

Najia rubbed her forehead in exasperation. "Mummy, you don't understand."

"Don't I?"

"Yaz has made 'friends' with an _alien_ ," Najia exclaimed. "An alien woman with a _spaceship_ ," she continued, jabbing a hand in the general direction of where she'd stomped out of the TARDIS. "She drags Yaz along on idiotic adventures that _will_ get her hurt." She let her hand fall, acknowledging futility. "I can't even believe how ridiculous that sounds."

Umbreen only nodded. "I met an alien, once."

"I keep telling you, that's just how kids _dress_ these days," Najia sighed.

Umbreen sipped her tea, ignoring her. "Lovely blonde woman. Thought she was quite mad."

Yaz stiffened, flicking her gaze between the other two women. Her grandmother gave her a bright, unreadable smile.

"What if something happens to Yaz on some distant planet? Will we even get a text to tell us she's never coming home?" Najia continued. "Not to mention that _none_ of this nonsense can ever go on a CV!"

Umbreen set her tea down with finality, the clatter of cup against saucer effectively ceasing Najia's ongoing rant. "Yasmin chooses her friends with great care," she said briskly. "You have always trusted her to be good, and brave, and smart, and you were always right to do so. And you have always known her world would be larger than Sheffield."

Najia leaned against one of the kitchen chairs with a sigh, and dropped her head forward in an evident combination of frustration and worry.

"Yasmin, dear," Umbreen said by way of summons, gesturing to draw her granddaughter closer.

Yaz immediately stepped to her side and took her hand. "Yes, Nani?"

Umbreen smiled up at her, then reached up to pat her cheek. "Tell your Doctor I said hello, will you?"

"I will."

"Be good, and brave, and smart, and look after her. I know she'll look after you."

Yaz's eyes immediately swam in tears. "Yes, Nani." She bent to give her grandmother a hug, then turned to her mother. "Mum..."

Najia straightened, and swiped moisture from her eyes. "I just want you to be _safe_ ," she insisted.

"I know," Yaz said. "But we do amazing things. We help so many people. And the Doctor..." She paused, trying to find the right words. "She's _incredible_. I'll never know anyone else like her, and every minute I spend with her is worth all the risk."

Najia studied her, seeking the additional meaning that statement might hold. Eventually she gave up with a shrug, and took her daughters hands. "Promise me you'll remember your family. _Promise me_ you'll be careful."

Yaz wrapped her in a hug. "I will. I love you, Mum," she whispered. She pulled away and smiled down at her grandmother. "I love you, Nani."

"I love you too, _Beti_ ," Umbreen murmured. "You'd better get back before that mad woman tries to run away without you."

She actually hadn't thought of that. The Doctor might well try to sneak off and leave her behind in some ill-advised bid for her safety. Yaz grinned and bolted out of the flat. She couldn't wait for the lift, instead flinging herself down the stairs, then bursting out of the stairwell and panicking just for a moment before she caught sight of the TARDIS down the hill. She laughed in relief and crossed the remaining distance at a sprint.

When she got to the blue box, she discovered that the door was firmly locked. It had never occurred to her that the door _could_ be locked, since she was pretty sure the Doctor would actively complain about having to keep a key in her pocket.

She knocked, softly. "Hi, it's me. Mind if I pop in?" She wasn't sure if she was asking the Doctor's permission or the TARDIS'.

In any case, the door immediately sprung open, admitting her with a squeak.

* * *

By the time she found the Doctor hiding in her library, Yaz was absolutely worn out. It had been a long, emotionally fraught day, and she absolutely was not surprised to see the Doctor distracting herself with research.

The Doctor spun round, disheveled and awkward, when she noticed Yaz entering the room. She managed a tentative smile only after Yaz smiled first.

"You weren't going to be tragic and self-sacrificing and leave me with my family to try and protect me, were you?" Yaz asked.

"No," the Doctor lied immediately, then made a face and looked down, fussing with the loose binding on one of her books. "The TARDIS wouldn't let me."

Yaz exhaled a laugh, and patted nearest wall in gratitude before stepping closer. 

"Also Graham and Ryan were quite disagreeable about the idea," the Doctor added. She didn't look up even as Yaz moved to her side, casually sliding into her personal space. "Also, I _hate_ the idea of ever being without you," she concluded, miserably.

"Well, good, because it'd be daft to leave me behind," Yaz said. "I'd just have to come find you."

The Doctor gave her a sideways look. "I'm sorry about your mum," she whispered.

"Don't be. I'm not," Yaz replied. "I needed her to see this. I needed her to know how amazing you are, and how amazing my life is with you."

"Okay, but the thing is, she's not wrong," the Doctor insisted. "It _is_ selfish of me to let you stay, and the world _will_ be too small for you when you decide to go back."

Yaz nodded, considering that. "Can I ask you something? Why don't you spend this kind of time trying to convince Graham and Ryan to leave?"

At that, the Doctor straightened, turning toward Yaz and fixing her with an intense gaze. She seemed to consider several responses before she said, "I think you know why." Her voice was rough and quiet, and her eyes shone with obvious longing.

"Then you know why I'm staying," Yaz replied, equally quiet. She reached up and smoothed back the Doctor's unruly blonde hair, then pulled her into a heartfelt, sorely-needed hug.

The Doctor hugged her back, and tucked her chin against Yaz's shoulder. Eventually she disengaged again, with a bashful smile that Yaz happily returned, before she cast a quick look around.

"Got a comfortable chair around here? I am _knackered_ ," she murmured.

The Doctor frowned, evidently torn between keeping Yaz nearby and shooing her back to her quarters. "Do you want..." she started.

Yaz didn't even give her the chance to finish the thought. "Just need a nap," she said flatly. "And I'm not keen to leave you alone right now, if that's okay."

With suspiciously bright eyes, the Doctor nodded and set about finding the couch that she knew was absolutely against that wall under the enormous piles of dusty books. When she finally located it, she and Yaz set about clearing it, then the Doctor directed Yaz to get comfortable while she disappeared briefly to find the blanket knitted from avian yak hair farmed on Bharani Seven, gifted to her by the High Mistress of the Mountain House in hopes that she might win the favor of someone called Martha...

Yaz barely heard the rambling tale, instead enjoying the lilt of the Doctor's voice as she changed distance and direction about the library. She settled in under the blanket with a grin, then blinked her eyes open when the Doctor sat on the couch next to her.

"This all right?" the Doctor asked.

"I think my grandmother remembers you," Yaz said instead of answering. Her face creased in a sleepy, thoughtful look. "Some 'lovely, mad, blonde alien' that she met a while back."

The Doctor put on her most innocent face. "Well, there are loads of us about."

"Mmhmm. None as memorable as you, I think," Yaz said, dipping her head with a lazy smile. "She said to say hello." 

"We'll just ignore the inherent paradox of that statement that imperils the integrity of all space and time," the Doctor muttered. "Probably for the best." She tossed a thumb over her shoulder, indicating the substantial pile of books and notes behind her. "I'll be researching over there, 'kay?"

"What are you working on?" Yaz asked.

"Trying to figure out who blew up a space station near Tau Ceti in the thirty-third century," the Doctor replied.

Yaz smiled, freed one hand from under the blanket to find the Doctor's, and tangled their fingers together. "I knew you'd do that," she said, with a look akin to awe. "I knew you'd honor their memory and try to help."

The Doctor squeezed her fingers. "Well, that's what we do, right?"

Yaz only managed a faint hum in response as she tilted toward sleep. The Doctor stayed at her side for a minute longer, and pressed a gentle kiss to the other woman's forehead before returning to her work.


	2. Delirious, Burning Blue

**Summary for the Chapter:**

> Wibbly wobbly science and discovery, one step closer to the root of the mystery.
> 
> Also, flirting.

When Yaz woke a couple hours later, she opened her eyes and immediately sought out the Doctor, who was working at a table across the room. Rather than get up, Yaz snuggled a little deeper under the blanket and spent a moment indulging in Doctor-watching. It was so rare to catch the other woman so focused, so unguarded, so deep in thought...

... _so_ wearing a rainbow propeller beanie.

Yaz stifled a laugh as the Doctor puffed out a dramatic breath, pointed upward to make the propeller spin.

"You gonna keep watching me, or come help me analyze a crime scene, PC Khan?" the Doctor called out, giving Yaz a sideways look and a smirk.

Yaz grinned and hauled herself upright to join the Doctor at her desk. She stood behind the other woman and laid a hand on her shoulder as she took in the station schematics and manifests piled about.

It was casual contact, really. Barely more than friendly. Even so, Yaz felt the response deep in her gut when the Doctor curled into her touch like a cat, seeking the closeness. Yaz savored the reminder of mutual attraction, and let her fingers slide up to the just under the Doctor's hair, giving her a friendly scritch.

The Doctor hummed, low in her throat. "Good nap, then?" she murmured.

"Yeah," Yaz replied. She cast her eyes across the chaos spread out in front of them, and the illegible scribbles on a nearby chalkboard. Somehow _that_ bit of retro kit was particularly fitting. "How's your research?"

"Maybe good, maybe bad. Do you remember what they said they were studying at that station?"

"Lieutenant Flinders said they were observing tachyons from a binary system," Yaz said. "But I thought tachyons were only hypothetical."

The Doctor craned her neck about to give Yaz a profoundly curious look.

"I read up on Wikipedia," Yaz admitted.

"Should have figured," the Doctor said with a delighted grin. "They _are_ hypothetical, to twenty-first century Earth. Bit less so, later on."

Yaz frowned. "So, not-hypothetical particles that move really fast."

"Faster than fast. Faster than _light_ ," the Doctor elaborated.

"Does that mean they travel through time?"

The Doctor _vibrated_ , absolutely reveling in the experience of examining the intellectual puzzle with her companion. "Yeah. Do you know which direction?"

"Direction? Like backwards or forwards?" Yaz squinted, thinking it over, before realizing it was a trick question. "Both directions," she concluded, carefully, dredging up every bit of knowledge the Doctor had shared on the topic. "Because time itself doesn't actually go one way or the other."

"One hundred points to Yasmin Khan!" The Doctor bounced to her feet, yanked off the beanie, plopped it on Yaz's head, then stepped over to the chalkboard and drew a long, squiggly line that intersected in several spots. "Time isn't linear, except in the subjective experience of a person _within_ time. In actuality, time loops and wanders across itself and occasionally gets stuck in a Tuesday. But a tachyon - it doesn't know all that. It gets ejected from a singular point in space and time, and never changes course. Sometimes it crosses a known threshold of time, sometimes it moves forwards relative to that time, sometimes backwards, sometimes it shoots through perpendicularly in no time at all."

"Is that what we do, in the TARDIS?"

The Doctor shook her head, and continued scribbling on the chalkboard. "Little different for us. The time vortex lets us drop _out_ of time, then pop back in for the good bits. Like nipping off during the intermission at _Wicked_ , but coming back for the big finale. Tachyons skip between time, punch straight through the continuum, and show up somewhere else. _Their_ existence is linear, even if the rest of existence isn't." She took a step back, studying her work, which really amounted to little more than a mess. "Did you happen to follow all that?"

"I caught the part where you have a surprisingly deep knowledge of musical theater," Yaz said, giving her a pointed look.

With a flourish, the Doctor tossed her chalk into the tray at the bottom of the board. She wiped the dust from her hands and gave Yaz an easy smile. "Yeah, well. Remind me to take you to Oz, sometime."

Yaz smiled back, but was still distracted by unanswered questions. "If tachyons happen to bump into normal time at certain points, but aren't predictable, how do you observe them?"

"Ah. You can't, can only see the shockwave once they've gone. And even then, you don't know where it came from." the Doctor replied. "It's a paradox."

"But the station's entire mission..." Yaz continued, with a frown of confusion.

"Was observing a phenomenon that can't actually be observed," the Doctor concluded with a shrug, and an anticipatory look while Yaz thought further. "Especially not with thirty-third century human technology."

That didn't make sense. Yaz turned it over in her head, trying to figure out what she was missing. "So... they weren't _directly_ studying tachyons, but they were studying something coincidental to the fact that tachyons exist." She eyed the Doctor, who waited, expectant and encouraging. "They were measuring the effects of time travel? Even though they shouldn't have been able to?" She took that notion onward to its logical conclusion: "And someone blew up the station to cover it up."

The Doctor sighed and shook out her arms, deflating a bit as she wandered back to the table, then casually tread into Yaz's personal space. "I was hoping you would come to a different conclusion," she said. "That's disappointing." She shook her head a bit, realizing how that came out. "No, wait. _You're_ not disappointing. Quite the opposite. You're _brilliant_. Incredibly clever, actually. And absolutely right." She reached up and poked the propeller on the beanie still perched on Yaz's head, setting it to a brief spin.

"I learned from listening to you," Yaz said, nevertheless preening a bit at the compliment. "Even when you sound completely mental... or worried, like you are now."

The Doctor sighed. "You're good at this investigating business. You should be a copper." She quirked her eyebrows at Yaz and tried to smile, but it came off as a grimace.

Yaz waited, and eventually reached out with one hand to take hold of the Doctor's, and ended up hooking their fingers together. "C'mon now," she said. "You can tell me what's bothering you."

"Time travelers are trouble," the Doctor blurted.

Yaz gave her a fond smile, and tugged on her hand a bit. "Says the time traveler, who is _definitely_ trouble."

"So I would know," the Doctor concluded. She tangled her fingers more securely with Yaz's, which served as a pleasant distraction...

... for a moment.

Yaz took a breath, with a cautious expression that telegraphed her awareness of the unstable ground between them. "Doctor, I'm sorry that there's no 'polite' way to ask this - but why is it okay for _your_ people to have the ability to travel through time, but nobody else?"

The Doctor's entire face shifted, looking somehow sadder and more distant than Yaz could ever recall. "Well, that's just the thing, innit?" she asked. "My people would have been a great deal better off without that technology, that responsibility. It's like a curse." She paused, then cast a look at a high shelf across the room, where a worn blue book sat by itself. She sighed, and her eyes turned suspiciously glassy.

Yaz followed her gaze curiously, but managed to bite back all her new questions while she waited out the moment of melancholy.

"In any case, illicit, misplaced tech like what our friends were using on that station... that points to criminal activity. Like that Krasko, trying to cause as much harm as he could, just _because_ he could."

"So we'll find them and stop them," Yaz interjected, confident and bright.

The Doctor cocked her head at her companion, and seemed to suddenly notice how close they were standing. "Ah, Yaz," she murmured. "Thank you."

"For what?"

"For reminding me that time travel can also be a gift. Like what brought me to you." They stood there, drifting in each other's personal space, for a long, gentle moment. "Have I ever mentioned that you have lovely eyes?" the Doctor said, canting her head to get a better look.

"Um. No?" The word came out as a near squeak.

"Well, you do," the Doctor murmured. "Very kind and safe. Reason why I trusted you the moment we met."

Yaz shook her head, and fought the urge to avert her gaze and thus hide her eyes from the Doctor's apparent admiration. "I must be slow. You had me at that leap across the cranes."

"Did I, now? Partial to leaping? Noted." The Doctor gave her a mischievous look and turned, tugging on Yaz's hand. "Come along, then. Let's go look for some particles that don't exist and can't be detected. Compound impossibilities with Yaz? _So_ amazing."

* * *

The TARDIS shuddered in protest as it dropped into the time vortex, and the Doctor set the dial as far back as it would go.

Ryan ambled in to the console room and tilted his chin in greeting to Yaz, who was sitting on the step, waiting and watching. "We off on another mission, then?"

The Doctor flipped a switch, bringing a screen down from the ceiling. "We are scanning the entirety of time, in this... general vicinity."

"Yeah? Scanning for what?" Ryan asked.

"Absolutely no idea," the Doctor said absently.

"Sounds like fun," Ryan concluded. "Can I help?"

The Doctor didn't really answer, she just waved in the approximate direction of the scanner and grunted.

Yaz zoned out for an unknown number of minutes, barely listening to her friends' chatter as they peered into the unknown abyss of time. It was comfortable and weirdly soothing, in the same way listening to her parents putter around each other in their kitchen was. _This_ was her family, now, she realized. This was her home.

She was smiling when Graham peered in, curious about why the entire TARDIS was rumbling. He stepped past the Doctor and Ryan, not keen to distract them from... whatever.

"What are they on about?" he asked Yaz, quietly.

"There's a binary star cluster that - at some unknown point in all of history - started emitting tachyons. We're looking for it."

Graham pursed his lips. "Well, obviously," he replied.

Yaz snorted. "The problem is that the universe has been expanding since time began, so those stars, even after they formed, haven't exactly been sitting still."

"So this might take a while?" Graham asked.

At that, the Doctor started a circuit of the console, rolling her shoulders to relieve the tension of staring up at the sensor screen. "To examine eternity, even on a localized scale? Could take eons," she said.

"Good to know," Graham said. "I'll put the kettle on."

Yaz watched him leave, and tilted her head in thought. "Doctor, could we narrow 'eternity' down a bit?" she called. "We know our thirty-third century human friends got hold of illicit time travel tech. When would that have been available?"

The Doctor snapped her fingers. " _Brilliant_ , Yaz! We can totally skip ahead a few billion years. Hang on." She flipped a lever and twirled as the TARDIS spun off across the vortex.

A few minutes later, Graham wandered back in with a mug of tea, and took a seat on the step next to Yaz. "Nice hat, by the way," he said dryly, chuckling when Yaz remembered the propeller beanie still on her head. Once she was done taking it off, hiding it, and pretending not to be embarrassed, he asked, "So how's your mum?"

"Oh, she's fine," Yaz replied, and smiled gratitude his direction for thinking to ask. "Just wants me to be 'safe.' By which I think she means 'bored to tears.'"

Graham nodded, with a speculative look. "Nothing wrong with safe and boring," he said. 

Yaz scowled at him, ready to argue with yet another old person who wanted to convince her to leave the Doctor behind.

"I'm sure it suits some people," he continued. "But, turns out, if you play it 'safe,' you miss out on some of life's most worthwhile bits." 

Oh. Yaz let that sit for a moment, and felt her hackles lower. "Worthwhile bits like spending time with a mad woman in a blue box who can take you to anywhere in space and time?" she asked.

"Nah. Worthwhile bits like falling in love," he countered, with a sideways look. "Caring about another person so deeply that you're willing to bear the pain when life is eventually hard and something bad happens. It's still a risk worth taking." He lifted his mug in salute to an absent Grace, then poked Yaz in the knee. "And for _some_ of us, a risk worth taking for a mad woman in a blue box."

Yaz sighed, and curled into herself. "Tell _her_ that," she murmured, dropping her voice.

"I will if you want," he said, matching her lowered volume. "But I don't think she needs any convincing."

Yaz held out her hands, with a look of disbelief. "She tried to leave me behind in Sheffield," she hissed.

"No, she didn't. Not really. She'd convinced herself that you wouldn't be coming back. Got entirely wound up while Ryan and I told her she was daft."

"I wouldn't leave her," Yaz protested, aware that her voice was in danger of carrying across the room. "Especially not like _that_."

"Tell _her_ that," Graham countered. He grinned, poked her in the knee once more, then stood and wandered back toward the console to see what his grandson was watching.

Ryan had taken charge of one of the scanner dials, incrementally scrubbing their view forward in time. The screen blipped in nondescript dots and lines, occasionally fuzzing in static. It was incredibly tedious, especially to the humans who weren't even sure what they were watching.

Somewhere around the forty-fifth century, the scanner erupted in an explosion of vibrant color, then reverted back to lines and dots when Ryan accidentally dialed too far. He jerked in surprise and nudged back a touch. "Whoa. What is _that?_ " he asked.

The Doctor leaned over to study the readout. "I don't know," she said.

Yaz immediately pushed to her feet upon hearing the note of shock in the Doctor's voice. The universe didn't often surprise an ancient time traveling alien like that. "Should we go take a look?" she asked, not even sure what she wanted to hear in reply.

The Doctor spent a moment studying the sensors in clear apprehension. "Suppose that's our next step," she said finally. "Looks like a moon orbiting the fifth planet of the minor paired star. Everyone bundle up - gonna be a chilly one."

* * *

The Doctor hadn't been exaggerating about the cold. It burned in Yaz's lungs as she took in the thin, dry air outside the TARDIS. The moon was a nondescript blue rock with the binary stars hanging above as dual suns, both too far to offer the surface any real warmth. There were rocks and hills and snow as far as they could see, ridged here and there with channels carved by wind gusts that dragged snow across the ground in dramatic plumes.

Beside Yaz, Ryan bounced a bit to warm up. "At least I got the Han Solo coat," he muttered, tugging the blue faux-fur-lined hood over his head. "Since this is basically Hoth."

"It's called Baridi," the Doctor said. She squinted behind massive ski goggles. "Barely habitable."

"That part is fairly obvious, Doc," Graham muttered from behind a thick scarf wrapped around his face. "So what is it that caused those crazy readouts and made us come here?"

The Doctor lifted her sonic screwdriver into the air, and let it tug her arm in a direction that looked vaguely north-ish. "Should be a structure over there," she announced. "Let's get a closer look."

As they made their way over the snowdrifts, a faint rhythmic shrieking noise rose over the wind, the source of which eventually resolved into a dangling metal door, swinging wildly on its hinges, over and over. It was the entrance to a structure carved into the side of a hill, almost entirely shrouded from the outside by the blustery snow.

When they got inside, they unbundled only marginally to get a proper look around. The Doctor produced handheld lights from one of her prodigious pockets, easing a bit of the pall of what appeared to be an abandoned science lab.

The Doctor scanned with her sonic screwdriver, frowned at the results, then scanned again.

"It's not right, here," Ryan said, squinting as he tried to sort out the unease of the place. "D'ya feel that?"

With one last useless sonic sweep, the Doctor couldn't help but agree. "Not sure what I'm detecting," she admitted. "Everyone move carefully."

"It looks like the space station," Yaz murmured, sweeping her light across a wall with familiar computer workstations.

"Why build a lab here at all?" Graham asked. "They really went out of their way to find this place."

The Doctor didn't answer, but grit her teeth and led the way deeper into the facility. Yaz kept close behind her, feeling the other woman's worry roll off in waves. 

The lab had been abandoned for some time, and compromised by the weather for some time after that. A couple rooms were entirely consumed by snow drifts, muting the sound of their footsteps as they wandered deeper into the dark.

"At least there're no bodies," Ryan murmured.

That had caught Yaz's attention as well, and she wasn't sure if it was actually positive or not. She cocked her head, noticing that the ambient sound of their movement was changing, just before they crossed a threshold into an enormous, open space carved from the lunar rock. Their path transitioned to a gangway that crossed a large chasm, at the base of which swirled a confusing tumult of energy. Yaz shut her eyes and grabbed at the guardrail, suddenly dizzy.

"Ryan," she called in warning. "Don't want to come out here."

"Figured that out already," he replied, calling from behind the threshold of the door. "What _is_ that?"

"Dunno," Yaz answered. She split her eyes open just enough to locate the Doctor's shape just ahead, and reached out. "Doctor?"

"There's something painted on the wall out here," Graham said. "Ry, take a picture of that."

Yaz called to the Doctor again, and received no answer. She shuffled forward, her eyes squinted mostly shut. Her hand made contact with the Doctor's shoulder, right at the exact moment the other woman buckled at the knees and collapsed against the railing. 

"Doctor!" Yaz screamed. She clutched at the Doctor's coat, hauling her backward, away from the drop into the chasm below. She felt jarring commotion as Ryan and Graham rushed in alongside them to grab hold as well, and with combined effort they stumbled back through the door and collapsed to the snow covered floor.

Yaz shook off her remaining disorientation, dropped to her knees at the Doctor's side, and carefully turned her onto her back. The Doctor's face was dreadfully pale, almost gray, with a trickle of blood leaking out of her nose. Yaz looked up, sharing her horror with her mates, then she bent and checked the Doctor's pulse.

The faint, dual thumping rhythm under her fingertips nearly undid her. "She's still alive," Yaz breathed. "We have to get her back to the TARDIS."

"Get her arms out of the sleeves, and zip her into her coat," Graham said. "We can use it as a stretcher to drag her back across the snow."

Yaz nodded and moved to comply, teaming up with Ryan to get the Doctor bundled into as mobile a configuration as possible. At one point Yaz looked up as the furtive handheld light flashed across the wall, illuminating the symbol Graham had noted earlier, and felt a sick realization deep in her gut. Thanks to her studies aboard the TARDIS, Yaz recognized Gallifreyan when she saw it, even if she couldn't read it.

What had happened here?

"Right," Graham said. "Ry, you take point with the light. Yaz, you and I will slide her along. Try not to jostle her."

Yaz bent one last time, taking a moment to run her fingertips across the Doctor's cheek. "Stay with me," she whispered, before pushing to her feet, grabbing hold of a tied sleeve, and setting about the grim task of helping her friends drag the Doctor to her ship.


	3. Saudade

**Summary for the Chapter:**

> A whole lot of hurt/comfort.

Everything hurt.

Yaz had lost track of the number of times she'd stumbled, had stopped noticing the bitter cold burning her lungs, and couldn't even feel the wind whipping against her face. They had finally crested the last hill, and the TARDIS was in sight. 

Graham and Ryan had traded spots some time earlier, Ryan stuttering his steps with his long legs to stay at Yaz's pace as they dragged the Doctor across the snow.

"Oi!" Graham called, from his spot bringing up the rear. "She's moving!"

They set the Doctor down gently, and Yaz fell to her knees in the snow at her side. "Doctor?"

The Doctor turned toward Yaz's voice, and opened one eye. "Who invited the Sontarans to the coronation?"

Yaz shook her head. "I don't know what any of that means."

"Oh." The Doctor peeled open her other eye and squinted at her, then looked at the concerned faces of Ryan and Graham as they panted plumes of breath into the frigid air above her. "My feet are cold," she complained, with a petulant scrunch of her nose.

Yaz exhaled a faint laugh. "We're on Baridi, and you collapsed in the lab. Do you remember?"

The Doctor scowled, and for a moment Yaz wasn't sure she even recognized her companions. "Not Hoth?" she asked.

"Not Hoth," Yaz answered. She exhaled a shaky breath and let her head fall forward, profoundly relieved.

Graham leaned in and put a hand on Yaz's shoulder. "Glad you're okay, Doc. Gave us quite a scare."

The Doctor squinted, tilting her head back to see the silhouette of the TARDIS. "Not really okay, though. Feel awfully timesick," she said. She started squirming, as if to free herself of the confines of her makeshift coat-stretcher, before Yaz reached over to still her.

"Hang on, we're almost there," Yaz said. She gave Ryan a look, and on unspoken cue they hoisted the Doctor once more, pushing through the final distance to the waiting blue box.

The Doctor was muttering to herself, bits about a bad wolf, someone having been saved in a library, silence, and fish sticks. Yaz tried to keep an ear close enough to catch the discernible words, but figured they were mostly subconscious flotsam. 

At least, she hoped so.

They finally clambered into the TARDIS, and kicked snow from their boots. The Doctor waited, seated on the floor and uncharacteristically patient, while Yaz and Ryan freed her from the tangled mess of her coat. 

"Can you stand?" Yaz asked. She teamed up with Ryan to haul the Doctor up by her elbows when she assented.

"You said you're 'timesick?' What does that mean?" Graham asked.

The Doctor looked at him in a momentary daze. "Artron energy poisoning," she replied, eventually. She put her fingers to her lip and smeared the trickle of blood from her nose with a scowl. "That thing in the lab must be a fissure in time. Leaking badly, by the look of things." She kicked off her shoes, sending packed bits of snow skittering across the console room floor. "It's flinging out artron particles that are incompatible with the ones in this universe. Incompatible with _me_."

She took a moment to push her hair out of her face, looking back at the three humans who were watching her in concern. "Basically like a human flu," she concluded. "Gonna be right cranky here in a mo'." 

"How can we help?" Yaz asked. "Can we take you somewhere?"

With a dismissive wave, the Doctor spun on her heel, then promptly lost her balance and would have toppled over if not for Yaz's quick grip. "Just gotta ride it out for a few days," she said. "Put me to bed and I'll be right as rain in no time."

She staggered off, with her worried companions all in tow, muttering about rain being "right" and how nonsensical human expressions tended to be. Finally, she dragged herself into her room.

"Haven't been sick in _literal_ ages," the Doctor declared. "Forgot just how completely unpleasant it is."

She twisted, and yanked both her shirts over her head, then attacked the fasteners on her bra.

"Nope," Graham said quickly, before turning and disappearing back down the hallway. Ryan squeaked, then followed suit.

Yaz chased after the Doctor, picking up the discarded remainder of her frosty clothing. 

Eventually, amidst a fair amount of grumbling, the Doctor found a mismatched set of oversized men's pajamas and flopped into bed. Yaz set about fussing with blankets and pillows, determined to make the other woman as comfortable as possible.

"Don't mean to be a bother, Yaz. If you want, the TARDIS can take you lot home," the Doctor said, with her face half smooshed into a cushion.

Yaz shook out a blue quilt stitched with bold yellow stars, which she'd borrowed often enough to know was exceptionally cozy. "Yeah, that's not gonna happen," she said bluntly. She pulled the quilt across the Doctor and tucked it carefully under her chin. "We can keep ourselves occupied while you recover. Now, can I get you anything?"

The Doctor shook her head, looking up at Yaz with wide, vulnerable eyes.

"Water? Tea? Your favorite soup?"

"You know my favorite soup?" the Doctor asked. Her voice was small, unusually plaintive and sad.

As if Yaz could forget the positively _sinful_ noise the Doctor had made when she'd tried the dumpling soup on Etris Three. She paused, realizing worry had turned her tone short and impatient. She took a moment to smooth some mussed blonde hair away from the Doctor's face. "Of course I do," she murmured. She perched on the edge of the bed, and rested her hand lightly on the quilt over the Doctor's belly. "Are you _sure_ you're going to be okay?"

The Doctor nodded, seeming entirely lucid, if miserable. Yaz decided to take her word for it, and felt the tension of panic slip from her muscles, leaving her absolutely exhausted.

"You _scared_ me," she whispered.

"Sorry 'bout that," the Doctor whispered back. She wrestled a hand out from under the covers, waited for Yaz to curl their fingers together, then exhaled a tiny, contented sigh. "All better now."

Yaz let her eyes drift shut in relief, then lifted their intertwined hands to press a kiss to the Doctor's chilled knuckles. "Mind if I stay?" she asked.

For a heartbreakingly long moment, the Doctor didn't answer, then she dropped her gaze. "Would you?"

"Yeah," Yaz answered. "I'm not going anywhere."

* * *

Ryan checked in an hour later, waving one hand past the edge of the door and keeping his eyes firmly covered with the other until Yaz assured him that everyone's modesty was safely accounted for. 

He stuffed his hands into his pockets as he stood at a mildly awkward distance from the bed. "She looks okay, yeah?" he asked.

"Yeah," Yaz agreed. She carefully untangled her fingers from the Doctor's and stood, leaving her spot at the edge of the bed for the first time. She drifted over towards Ryan, stretching sore muscles while she led him far enough away to chat without disturbing the sleeping woman. Eventually they both leaned against a low wardrobe on the far side of the room. "Remember that glowing yellow... stuff... when we first met her?" she asked.

Ryan nodded. "Proper weird, that," he said.

"That was regeneration energy," she elaborated. "Her kind expend that when their bodies are about to die, to make a new body."

It hadn't occurred to Ryan to think the Doctor might be that gravely ill, and he swallowed against his own new anxiety. "She's not doing that now, though. That's good, right?" he asked.

Yaz nodded. "I think so, yeah." Still, she kept a keen eye on the Doctor's breathing, even from across the room.

Ryan watched them both, before bumping against Yaz. "So, the two of you, huh?"

Yaz blinked at him in alarm, then relaxed with a faint snort. "I don't actually know how to answer that."

He nodded, with a thoughtful frown. "Well, I bet your mum's happy. Even if you brought home a lady, at least she's a doctor," he said, keeping a straight face until she elbowed him, hard.

"Shut _up_ ," she said, shaking her head while he chuckled. She twisted her fingers together, and smiled when the Doctor exhaled the faintest bleat of a snore. "Her and me... it'd be weird, right?"

Ryan shrugged. "Yeah, a bit. But my nan and Graham - they were weird, too. Like, she was fine without him, _we_ were fine without him, so why keep him around?"

He was quiet for a moment, and could feel Yaz watching him. "She _was_ fine. But Graham made her happy, and they were good together, you know? It was different, but it was better." He huffed a bit, impatient with his own words. "I think you do that for her."

She leaned against him in grateful solidarity. "Thank you."

Ryan nodded, and decided to stop talking since he'd apparently managed to say the right thing. 

Eventually Graham came to check in as well, and together they kept vigil over their friend well into the small hours of the moon's lonely, frigid night.

* * *

Everything _still_ hurt, but this time Yaz figured she really should have expected as much.

She winced and rolled her shoulders, trying to work out the kinks left over from sleeping curled up on the floor alongside the Doctor's bed. She took a moment to wait in silence, until she caught the faint wheeze of the Doctor's breathing, then scrubbed gentle fingertips across the Doctor's outstretched hand and slowly got to her feet to look around.

Ryan was sprawled on the floor in front of the low wardrobe, playing on his phone. He gave her tiny, exhausted wave. Graham had stepped out sometime earlier to change and work on breakfast. 

The Doctor seemed to be breathing easily, and had shed the alarming pallor of the previous day. Lacking any other data about time lord anatomy or artron energy poisoning, Yaz decided that the morning's arrival was an important threshold, and the Doctor was truly on the mend.

It was hard, at that moment, in the warm, dim light of the Doctor's room, to see her as "alien." Yaz could only see a beautiful, troubled woman, hurting and desperate for companionship. It was nearly impossible to see the ancient time traveler who had been hardened by unfathomable loss across unfathomable time.

All at once, Yaz was overwhelmed by sadness, certain that no matter the depth of her feelings, she couldn't hope to offset that loneliness, couldn't offer the Doctor anything but brief, poignant company.

How could that possibly be enough?

She folded her arms, retreating into herself just as Graham leaned back into the room bearing tea and bland biscuits.

"Oh good, you're up," he said, pitching his voice low. "How about I take a shift with her while you two get some food, then we'll see about some more comfortable furniture in here?"

Yaz nodded, grateful to have a plan. She offered Ryan a hand up, and he groaned at the stiffness in his long limbs.

At the sound the Doctor stirred, turned her head and muttered something that sounded like "Stormageddon, Dark Lord of All" and "his catastrophic nappy."

Ryan and Yaz shared a look of alarm, before simultaneously dipping out of the room.

"We'll be back after breakfast," Yaz said quickly.

"Yeah, good luck with _that_ , granddad," Ryan added.

Graham sputtered a brief protest, but was left alone with the Doctor in short order. "Um. 'Stormageddon,' was it?" he asked.

"Goes by 'Alfie,' now," the Doctor mumbled, still mostly unconscious.

"'Course he does," Graham said, with a shrug. He held out the biscuits with a coaxing look, hoping to distract from any further mention of Alfie's nappies. "Think you can manage to eat something?"

* * *

After a shower, a nap, and a bowl of cereal, Ryan stood in the TARDIS' door, pulled his Han Solo hood over his head, and tugged on ski goggles. He surveyed the alien panorama for a dramatic moment, then bounded out into the cold to start building an army of snowmen.

* * *

Even though they'd divided their time to keep eyes on the Doctor's recovery, Yaz couldn't stay away for long. Graham seemed to understand, and left her alone after they'd teamed up to carry an overstuffed armchair into the Doctor's room.

For a few minutes, Yaz sat, watching the Doctor anxiously. Her feet bounced against the floor, and she blew out an exasperated breath while she tried to settle in to wait.

"Lot of fidgeting going on over there," the Doctor muttered.

Yaz leapt to her feet and hovered at the bedside. "Oh no, I'm so sorry. I didn't mean to disturb you."

The Doctor pried open one bloodshot eye and gave her a wan smile. "'Salright. Just never knew you to be a fidgeter."

"Only when I'm worried about you," Yaz said, with a self-conscious shrug. "Do you need anything?"

"A shower," the Doctor said, miserably, as she shivered under the covers. "You're lucky you can't smell artron reactions. It's not pretty."

"Okay." Yaz leaned backward and considered their options. Maybe she could ask Graham and Ryan to help...

The Doctor sat up, slowly, then paused to breathe through a bout of dizziness. Yaz immediately reached to grab hold of the other woman's shoulders to keep her steady, and for a moment they just looked into each other, eventually coming to an unspoken understanding.

Yaz helped the Doctor to the edge of the bed, then slung the Doctor's arm over her shoulders to guide her to the bathroom. There, she helped the Doctor strip, then pushed her under a steaming spray of water and stayed just outside, making sure the other woman stayed upright until she was done scrubbing clean.

When the water stopped, she immediately wrapped the Doctor in the biggest towel she could find, and chafed her dry. 

As intimate as this all was, Yaz was careful to keep her face neutral, not letting her eyes wander. Her _friend_ needed her help, and this was not a time for indulging in curiosity about the expanse of soft, exposed skin. She found another pair of mismatched pajamas, got the Doctor dressed, and escorted her back to bed.

There, the Doctor was pliant and dazed while Yaz blotted her hair dry and gently brushed it.

When she was done, the Doctor looked up at her with possibly the most pathetic expression Yaz had ever seen.

"I _hate_ being sick," the Doctor declared. She turned just far enough to faceplant into her pillow, and promptly fell back to sleep.

* * *

The next day, Yaz wandered into the console room. "Um, hello? TARDIS?" she called. She made a face at how absurd that sounded, but pressed onward. "The Doctor's told me she's from a planet called Gallifrey," she began. She pulled out her phone, and swiped to find the picture of the symbol they'd found in the abandoned lab. "This is from there, right? Her native language?" She put the phone away. "I need to translate it. Can you help me?"

After a moment, the room's usual ambient hum dropped, and the lights dimmed to near-dark. The main hallway transitioned to a vibrant orange. 

Yaz approached with a curious look, then followed corridor after corridor, each lit in the same inviting warmth. She walked for several minutes, winding deep into the heart of the ship. She realized as she went that she was traversing across generations of the TARDIS itself, discovering progressively older and older layers of the ancient vessel.

Finally, she found herself in a plain, gray room with a desk and a chair. There was a book on the desk, with dog-eared pages hanging out of the worn binding. Yaz stepped closer, and ran careful fingertips across the book's cover. 

"Is it okay for me to look?" Yaz asked, in a hushed tone that matched the reverential feel of this unexpected place. The air was still around her, and she felt the urge to hold her breath. 

The light in the room dimmed, leaving only a single shaft of orange light illuminating the book. She took that as a form of permission, and picked it up, then followed the lit corridors back to the main living areas. 

When she relieved Ryan for her shift watching over the Doctor, she snuck the book into the room carefully, somehow sensing how precious and private it was, and that the TARDIS wouldn't have shared it with just anyone.

Yaz let her eyes linger on the Doctor's somnolent form, and hardly noticed her own reflexive smile as she bent over and rearranged the blankets to a more agreeable configuration.

She brought a lamp over to the armchair they'd relocated to the Doctor's bedside, carefully cracked open the book, and set to work.

* * *

If Yaz hadn't already known the Doctor, she would have suspected the book described a complex descent into madness. Even with the appropriate context, the fractured changes in personality and disjointed recollection were quite unsettling.

There were multiple styles of handwriting, and multiple languages that Yaz was only able to read by the TARDIS' helpful telepathic assistance. As she read she started piecing together the many lives of an alien who agonized about their place in the universe, who felt a responsibility to so many.

The pages had Gallifreyan glyphs in the margins, fragments of larger thoughts abstracted against languages that had long perished from existence, and some languages not yet spoken by a living being. She traced her fingers around the circular symbols, appreciating the vocabulary as well as the complexity of time and tense.

She pulled out her notebook and her phone, and started transcribing the glyphs from the lab, over and over. Somehow, the pattern tugged at her, latching onto a part of her mind she could only _just_ recognize.

With practice, she could reproduce the symbols with ease. The notches and radiating lines caught her fingertips as she traced them, over and over again.

That night, she dreamt of the abandoned lab, and the terrible, swirling energy it held secret.

* * *

_Unending._

After countless hours of poring through the Doctor's notes, and mulling the abstracted musings on seventeen different Gallifreyan tenses, Yaz finally realized: There _wasn't_ a tense. The subjects of the symbols from the lab simply _were_ , across time and space. Constrained and yet infinite.

She sat back, and noticed she was due for her shift to look after the Doctor.

"She's been waking up more often," Graham said when Yaz arrived. "Was nice enough not to look too disappointed when she saw it was me keeping her company." He smirked, and puttered toward the exit. "She'll be glad to see you."

Yaz hummed and nodded, hoping that would be a sufficient response. Once Graham had left, she pushed the chair carefully to the far corner, under a light source. The room felt claustrophobic and stifling as she fought through competing waves of emotion. 

She desperately wanted the Doctor to wake up and return to her usual energetic self. She desperately wanted the Doctor to smile at her in that private way that made her insides burn in anticipation. At the same time, she was also keenly aware that they were quickly nearing an inflection point in their relationship, and she wasn't sure she'd be happy about the outcome.

The Doctor's journal did little to give her confidence. As she read, Yaz saw an increasing desperation, a growing melancholy manifested in lost companions. It absolutely broke her heart, knowing that the woman she knew as the Doctor was the culmination of every loss suffered before.

She pulled out her notebook and returned to her translation.

Sometime later, Yaz looked up from her work, quite unsurprised to see the Doctor awake and watching her. "Hi," she said, with a smile.

"Hi," the Doctor replied. Her expression turned wistful as she stirred under her blanket. "Why are you so far away?"

It wasn't the time to bring up the mess of conflicting feelings raging in her head, so Yaz shut her notebook and stood to wander across the room. "I didn't want to bother you," she murmured. "Do you need anything?"

The Doctor shook her head. "It's better when you're close," she said.

"I'll bring the chair back over," Yaz began, before realizing that the other woman was shifting, moving to the far side of the bed in clear invitation. Yaz froze, and flicked her eyes up to meet the Doctor's.

The Doctor looked back at her with such profound, obvious yearning, Yaz felt her heart absolutely shatter. In that moment, she had her answer: she would do _anything_ to bring this woman as much joy as she could, for as long as she was able.

Yaz took a deep breath, and with careful, deliberate movements, she set her notebook and the journal on the bedside table, then kicked off her trainers and slid under the covers. When she dared meet the Doctor's eyes once more, she saw relief and a drowsy kind of triumph.

"Napping with Yaz, _amazing_ ," the Doctor murmured with a smile.

_i love you i love you i love you i love you_

The words raced like wildfire in Yaz's brain, the emotion plain and clear for the first time she'd cared to notice. She exhaled carefully, and reached out to find the Doctor's hand under the covers.

"I'm here," was all she said. It was all she could manage.

* * *

Yaz hadn't meant to fall asleep, but found herself waking up sometime later, curled on her side next to the Doctor, who was awake and sitting up against the headboard.

The Doctor looked over and smiled. "Mornin'," she said.

"Is it morning already?" Yaz asked. She blinked hard and stretched.

"No idea," the Doctor replied easily. She held up Yaz's notebook. "But you've been busy."

Yaz froze, feeling irrationally caught out. She watched the Doctor carefully, trying to decipher her reaction.

"Where did this come from?" the Doctor asked.

Yaz sat up. "It was painted on the wall in the lab. Ryan got a photo of it."

The Doctor nodded absently. "And you found my journal?" she asked.

"The TARDIS showed me," Yaz explained. "I needed help to translate the symbols."

The Doctor nodded a bit more, bemused. "You were doing well," she said, then gave Yaz a sideways look and a relaxed grin. "Which isn't surprising, at all."

"What does it say?" Yaz asked, relieved and eager to understand the mystery.

"Roughly translated, it says, 'The Timeless Child vanquishes the Oncoming Storm,'" the Doctor recited, with a speculative tilt of her eyebrows.

Yaz sat up, intrigued. "Wait. 'Timeless Child?'" she repeated. "Didn't those cloth creatures say that..."

"On Desolation," the Doctor confirmed.

Yaz waited, but the other woman offered no further revelation. "So what does _that_ mean?"

"I don't know," the Doctor said. She frowned and set aside the notebook, then produced a plate of sandwiches she'd been keeping on her side of the bed. "Graham brought us snacks, though."

With an impatient noise, Yaz cast out a hand, smacking lightly against the Doctor's arm. "That's _it?_ "

The Doctor munched on a sandwich, and shrugged. "It'll still be a perfectly good mystery after we eat," she said, reasonably. She offered the plate to Yaz with a teasing look.

Yaz rolled her eyes, but took a sandwich and tucked in. "You're feeling better," she said, almost in question.

The Doctor nodded. "Still wobbly." She leaned toward Yaz's warmth. "But you lot took good care of me. Thank you."

They settled back under the covers, curled against each other. The Doctor finished her snack and retrieved Yaz's notes, then started to describe the circular tangle of language for Yaz's benefit, tracing the glyphs with her finger just as Yaz had.

"You already figured out the tense," the Doctor murmured. "Very unusual. Both the 'child' and the 'storm' are pan-temporal." She pointed to a notch that crossed two concentric rings. "This means it's an honorific."

"'Timeless Child' is a title?" Yaz asked, peering in with avid fascination. She pointed at a similar notch across jagged half-circles. "Does that mean the 'Oncoming Storm' is a title, too?"

The Doctor chuckled ruefully. "Could say that," she said. "A few of my past selves had a flair for the dramatic."

Yaz jolted. "Wait. You? _You're_ the Oncoming Storm?"

"On at least fifteen different worlds," the Doctor said. "Including Skaro, home to the Daleks. Although, I can't see them leaving graffiti about in a human lab. Not really their style. Probably not a message from them." She thought for a moment more, then shrugged. "Guess we'll have to study that fissure to learn more."

"You're awfully calm about all this," Yaz observed.

The Doctor shrugged. "All we can do is wait and see. Might not be anything bad. Might even be amazing."

"How could being 'vanquished' by a child be amazing?"

"You never know," the Doctor concluded, with an inscrutable look. "And anyway, why waste a perfectly good whatever-time-this-is by worrying? I woke up with a pretty girl and some lunch. There are worse ways to start the day."

Yaz blushed, and looked down to hide her ridiculous grin.

"Yaz," the Doctor whispered, drawing her eyes back up. "I'm not... I'm used to being alone, through the worst of times. I can't tell you what it meant to have you here," she said. She tilted her head down to peer at Yaz with an intense look through her lashes. "Thank you."

Those three words were back, burning across her tongue. Yaz took a breath, and smiled. "Of course," she said quietly. "Would you teach me more?" she asked, pointing to the Gallifreyan script.

"That could take a while," the Doctor warned. "The oblivion tense alone might take years."

Yaz shrugged. "Seems like a good way to spend whatever-time-this-is, with a pretty girl and some lunch," she said, settling in. "Let's get started."


	4. How Souls Mate

**Summary for the Chapter:**

> Feelings, science-y exploration, and some payoff for the slow burn. :)

After a lively lesson in Gallifreyan grammar, the Doctor had tucked herself against Yaz's shoulder and drowsed to the sound of the younger woman's voice while she told stories from secondary school. Yaz smiled as she recalled a particular lit course, explaining how she'd practice Shakespearean dialogues with her friends, playing Orsino to their Viola, and Orlando to their Rosalind.

"Were you good at acting?" the Doctor asked.

Yaz chuckled. "Absolutely not. I just liked romancing the other girls."

"Charmer," the Doctor said, with a smile.

Yaz curled a hand up to card her fingers through the Doctor's soft hair. "What made you the 'Oncoming Storm?'" she asked.

The Doctor hummed, distracted from the question by the gentle touch. "Oh, you know. Did terrible, drastic things to end a war here and there. Thought I had to, thought I was the only one who could."

Yaz waited, feeling the Doctor's hesitation, and continued gently stroking her hair.

"Sometimes I miss being that person," the Doctor murmured. "I miss being so sure, even when I was so wrong."

In the ensuing quiet, Yaz fretted and sought in her head for something to help. "You're still sure about the important things," she said, finally. "You want the universe to be beautiful and fair, and you try to fix it when it's not."

It must have been the right thing to say. The Doctor relaxed, and tossed an arm across Yaz in a lazy embrace. "Thank you," she murmured.

"Always," Yaz said immediately, glad the Doctor couldn't see her blush. "Is it okay if I keep reading your book?" she asked.

"I 'spose so," the Doctor said sleepily. "Did you find the bit I wrote about you?"

"No? What does it say?"

The Doctor grinned. "You'll see."

* * *

It was another day before the Doctor was up and about, and she credited the healing power of toast.

At least, she said as much for Ryan's benefit, since he was so chuffed about bringing them breakfast. Privately, she was convinced that Yaz's presence was far more therapeutic.

When Ryan arrived with a pile of overdone toast and a knowing grin, both women had already taken turns showering and changing, and were sitting together casually on the Doctor's bed. Yaz leaned back against the headboard, and the Doctor sat perpendicular to her, propped on her hands with her legs bent across Yaz's.

While they ate, Yaz lost herself to the notion that it would be so easy to fall into this kind of life at the Doctor's side, curling together in the dark, telling each other secrets, and occasionally saving the universe. As stressful as these days had been, she savored the new degree of closeness they'd forged. She was loathe to actually talk about it, in case it suddenly went away, but yet...

"You know, I really like being with you like this," Yaz said. "Obviously not the part where you were ill, but all the rest of it."

"Mhm. Me too," the Doctor said. She lifted her feet, one at a time, pointing her toes to stretch and feeling the strength slowly returning to her limbs. "Don't tell Ryan, but snuggles with Yaz are way better than toast."

"I'd do anything for you," Yaz continued, mostly ignoring the Doctor's digression. "And I know you'd do anything for me."

"'Course I would," the Doctor agreed, light and easy.

Yaz pursed her lips, and took the final leap. "Do you think you could you be happy, with a human? Would that be worth it, even if it's just for a little while?"

The Doctor went very still and gave her a thoughtful look. "Depends on the human," she said, carefully.

The moment had grown a bit too intense, and Yaz wasn't sure she had the nerve to push further. "Well, Graham, obviously," she replied, with a wry shrug.

The Doctor snorted a positively undignified laugh, triggering Yaz's giggle in response.

Yaz shifted, pulling her legs up and turning so that she could lean closer, and summoned one more scrap of bravery. "I'd never want to hurt you, and I'd understand if you didn't want to risk it," she whispered. "But I think, maybe, we could be amazing." 

The Doctor mirrored the shift in posture and gave her a worried look. "Yaz..."

"And I think, maybe, you might feel the same." At that, Yaz's courage ran out. She moved away from the Doctor's warmth, but leaned back briefly in to press a kiss to the other woman's cheek. "Think it over," she said, before slipping out of bed and padding back to her own room to quietly freak the hell out.

The Doctor spent a long time staring into empty space, unable to do anything other than what Yaz requested. 

So _much_ thinking.

* * *

More food was _not_ appealing, the Doctor declared later, with a slightly ill expression when Graham offered to make her an omelette. Beverages, specifically hot cocoa, were as adventurous as she could manage.

She did, however, concede to extra marshmallows.

The Doctor greeted Ryan in the console room, then puttered around while slurping her cocoa, eyeing the mess she didn't remember making while she wandered toward the door, intending to get some fresh air.

She opened the door, peered out, then shut it promptly and spun on her heel. "I don't want to alarm you, but I think we may be under attack," she said.

Ryan waved in apology and jogged over. "Oh, no, sorry, those are snowmen."

"Snowmen?" The Doctor opened the door again, and raised her eyebrows as she looked over the dozens of figures of various sizes and poses.

"And snow women," Ryan said, as he wandered up behind her. "Some snow TARDISes. Also snow frogs." He pointed at a cluster of smallish critters with a grin.

The Doctor was both impressed and a bit horrified. "That's an awful lot of snowthings, Ryan."

"I got bored," he explained. "Graham and I ran out of things to talk about, and you and Yaz were, you know. 'Busy.'"

With effort, she ignored the poke about Yaz. " _Promise me_ that you won't make any snow angels," she said, grabbing hold of his sleeve and giving him an intense stare. "This is very important."

He shrugged. "Okay, yeah. I promise."

"Good." She sipped her cocoa again and looked around the console room. "You got bored in here, too?"

He winced. "Right. I was using the scanner thing, you know? I started wondering - what if the fissure was like an eclipse? And if you had the right kind of lenses, you could look at it safely?"

"You were building a temporal filter?"

"Yes, that!" Ryan said, gesturing in triumph. "You can totally filter radiation readings with the TARDIS sensors," he continued, pulling up the screen that had shown them the fissure in the first place. With a few switches, he enabled a filter, then another and another until the anomaly resolved into an orderly spherical pattern, reminiscent of Earth's magnetic fields. "That was pretty cool."

The Doctor nodded in approval. "You're right, that _is_ cool."

"But that was far as I got," he concluded. "Dunno what to do next."

The Doctor beamed at him. "Fifty points for Ryan Sinclair," she declared. "And an even hundred if you help me build the portable version."

* * *

After a few hours had gone by, Yaz finally ventured from her room. She stopped by the galley for a snack, relieved that no one was around.

She was simultaneously incredibly proud of herself for putting herself out there and dreading what was to come. If the Doctor turned her down, she was hoping they could still be friends, and could continue traveling together.

She could hear the activity in the console room from down the corridor, and couldn't help but smile...

... which was how the Doctor first saw her when she looked up from a mess of wiring that most definitely posed a fire hazard.

The Doctor smiled back, tentative but sincere. Yaz felt the last of her dread float away. They were gonna be okay.

"What's all this?" Yaz asked.

Ryan popped up from behind the console. "We're building a portable temporal filter," he announced. "So we can get a closer look at the fissure in the lab. Based on _my_ design," he added, looking enormously pleased with himself.

Yaz grinned in response. "How many points is that worth?"

" _So_ many!" he replied. "Might even retake the lead over you."

The Doctor shook her head subtly, letting Yaz know that wasn't likely.

"But we only have material for one sensor pack," Ryan added. "I sorta broke one already."

Yaz did the math from that statement, and met the Doctor's suddenly stormy gaze. So much for that tentative good will.

* * *

"You _can't_ go," Yaz argued, as she stalked after the Doctor, down the corridor back toward her room.

The Doctor spun around and lifted her eyebrows delicately, unused to being ordered about in any capacity. "I'm _sorry_? What can't I do, on my own ship?"

"That radiation almost killed you..."

"That's more than a _slight_ exaggeration," the Doctor scoffed.

"And it's idiotic to risk further injury when you have three humans who can go in and not be affected," Yaz said.

"Right. And which of you..." the Doctor trailed off, seeing the conclusion in Yaz's eyes. "No. Absolutely not."

"You _know_ I'm the best choice."

"The 'best' choice is leaving that thing alone and getting far away from this place," the Doctor said, casting her arms out in an indifferent shrug. "Brilliant! We'll just leave. _What_ temporal anomaly? Didn't Graham say he wanted a fruity drink?"

" _Doctor!_ " Yaz snapped. "People died because of that thing. We owe it to them to find out why, and you know it."

The Doctor bit back a dozen different angry responses, then stormed into her room and slammed the door shut.

* * *

Yaz stomped back into the console room in frustration. Ryan kept his eyes on his wiring work, pretending he hadn't heard the entire argument.

Graham, on the other hand, had no such compunction. He walked in with his hands held wide. "What was all _that_ about?" he asked. "I could hear that all the way in the study."

Ryan whistled. "Mom and Mom are fighting," he joked, before unsuccessfully dodging the punch Yaz aimed at his arm.

"All right, Yaz?" Graham asked. 

She exhaled loudly. "Yeah. Help me get this thing on?"

"You sure?" Ryan asked.

She just gave him a look, then sighed. "Yeah, but if something happens..."

"Nothing's gonna happen," he insisted immediately. "Don't pull that."

"Seriously, Ryan!" she hissed. "You can't let her anywhere near that fissure. It'll kill her."

He made a face, and concentrated on securing his micro camera to a helmet. 

"Promise me you'll keep her away from it," Yaz said. She looked over to Graham. "Both of you."

Graham sighed. "You know as well as we do that the Doc does what she wants," he argued.

"Promise me," Yaz insisted. 

After a moment, Graham nodded. Ryan gritted his teeth and agreed as well, just as the Doctor re-emerged from her pout. She shuffled over to help Ryan with the final connections, but couldn't quite meet Yaz's eyes. Her subdued behavior was the only concession she made to the earlier argument.

The setup consisted of the helmet with sensors and camera, a backpack with a battery pack and antenna, and a control strip with switches strapped to Yaz's arm. The Doctor took her time explaining the temporal emitters that would mostly cancel out the non-native artron effects in a small bubble around her, then carefully put the helmet on Yaz's head and eyed the TARDIS controls to make sure the telemetry was coming through.

After a few adjustments, there was nothing further the Doctor could do to stall. "You'd best come back in one piece," she admonished. She attached a communicator to Yaz's throat, then spent a moment carefully sorting the collar of Yaz's coat under the sensor straps. "We have a conversation that needs having."

"We do," Yaz agreed with a tiny smile. She took a deep breath, nodded to Ryan and Graham, then headed back out into the cold.

The lab looked much as it had before, though the weather had erased all trace of their earlier passage. 

She was glad of the periodic sensor reports over comma from Ryan, since his voice helped dispel the eerie gloom.

"The readings are starting to get messy," he announced, as she headed toward the corridor that lead to the chasm.

"Right, turning on the filters," she replied. She flipped the switches in succession, noting the growing hum from the electrical bits strapped to her back.

"Thats better," Ryan said. "Think you're good, Yaz."

She took a breath and started moving again, and shined a light across the Gallifreyan glyph on the wall. She rested her hand on it for a moment before stepping through the doorway and onto the gangway over the chasm.

The fissure was still there, but it seemed muted, less chaotic. She squinted as she looked closer, then gasped. "There are people down there!" she cried.

"Not people," the Doctor replied immediately. "Not from our dimension, anyway. They're echoes from a different iteration of spacetime."

Now that she was looking more closely, Yaz realized she could see _through_ the figures hovering at the edge of the fissure. She shivered a bit, then looked ahead to the ladder at the opposite end of the gangway. "I'm heading down," she announced.

"Doing okay out there, Yaz?" came Graham's voice.

"Yeah," she said. "The filter really helps."

"One hundred points," Ryan whispered. Yaz could practically see the fist pump.

She descended the ladder quickly, starting a bit when one of the extradimensional figures seemed to cross through her path. Once she was on the chasm floor, she skirted a generous radius from the outer edge of the fissure's event horizon. "Are you seeing this?" she asked.

"It's _beautiful_ ," the Doctor declared.

Yaz grinned and looked around. There was a desk off to one side where several of the ghostly figures congregated, studying bits of reality only they could see. She wandered over, then reached in between them to pluck an object off the desk. "It looks like that thing Krasko had, back in Alabama," she said, as she held it up for the camera.

"A vortex manipulator," the Doctor concluded. "I _told_ you time travelers were trouble."

Yaz tucked it into her pocket. "These dimensional echoes," she began. "Are they from the future or the past?"

"Neither. Or both," the Doctor replied. "Hard to say."

"Can they see me?"

"Not without equipment to filter out the different convergences, like you're doing," the Doctor said. 

Yaz studied the fissure, losing herself for a moment in the hypnotic ebb and flow of energy. "So what's inside there?" she asked.

The Doctor started to reply, then got distracted by a spike on one of the sensor readouts. "Yaz, gonna want to get some distance from that thing."

Yaz frowned and backed away a few steps. "Could I toss the camera inside?"

"Only if you want to buy me a new camera," Ryan argued.

The Doctor wasn't listening, instead feeling a prickle of alarm across her skin that mirrored the flickering sensor gauges. "Yaz, get out of there," she ordered. " _Now_."

Yaz reacted immediately to her tone and stepped back toward the ladder, even as she unhooked the helmet and pulled it off her head. Once she was back up on the gangway, she stopped directly over the fissure and tossed the helmet and camera toward the event horizon. 

The coinciding blast of energy obscured whether or not she'd hit her target.

With an eruption of sparks, the feed from Yaz's sensors cut out at the TARDIS console. The Doctor, Graham, and Ryan all ducked, then looked up in horror at the blank monitors.

"Yaz," Ryan breathed, then leaned into the microphone in the console. "Yaz!"

After seconds ticked by with no response, the Doctor rounded the console, heading for the door. "I'm going," she declared.

Graham chased after her. "Doc, you _can't_ ," he said. "That thing will kill you."

"Don't care," she snapped. "Are you coming?"

Graham looked back to Ryan, who stood at the console, sad and helpless.

"She made us promise," Ryan said.

"Promise _what_?" the Doctor demanded.

"That we wouldn't risk it if something happened to her," Graham replied. "That we wouldn't let _you_ risk yourself."

The Doctor glared at them both in simmering anger, then she stepped around Graham toward the door. She took hold of the door handle, which didn't turn.

"Oh no you don't," she muttered, before turning back to the console. "You let me out, _this instant_."

At that, the entire TARDIS went dark, dropping into standby low-power mode. The only visible light streamed in faintly from the windows in the door that stayed firmly shut.

The Doctor whirled in disbelief, and pounded on the door, wrenching herself against the handle while uttering a low, terrifying growl that eventually rose to a wail as she slammed her fists into the door.

Graham and Ryan hurried up behind her, grabbing at her swinging arms to haul her backward. She struggled in their shared grip, then gave up and went limp against them.

"Let me go," she keened, low and broken. Ryan rested his head against hers and fought tears. Graham just clung to them both.

When the fight had drained from her depleted muscles, the Doctor slipped to the floor, eventually settling in the doorway among the dying beams of the moon's dual sunset.

Graham and Ryan stayed nearby, hanging back in the shadows and waiting.

An hour went by.

Suddenly, the TARDIS hummed, and the lights rose again. They all cast a brief look around before the door popped ajar with a squeak.

The Doctor started, then leapt to her feet and yanked the door fully open.

Yaz stood outside, knee deep in the snow, ethereal and statuesque among the snowperson army. Her eyes glowed a brilliant blue, before she blinked and focused on the three faces staring back at her from within the TARDIS.

"Hey, sorry about that," Yaz said. "Feel a bit weird."

The Doctor lurched forward and clutched at the other woman, then pulled her inside, hugging her so hard it knocked the air out of them both.

Within moments, Graham and Ryan joined in for a joyful, relieved group embrace.

* * *

"Oh," the Doctor said, reading the output from her sonic screwdriver.

Yaz was sitting on a raised bed in the medbay, and prodded the Doctor with her foot. "Oi. You're not allowed to do that," she complained. "Human patient here, needing actual words."

The Doctor looked up at her, a bit startled, a bit guilty, and still quite a bit unsettled by the interminable hour she'd thought Yaz lost for good. "Right, sorry. Bit of explanation warranted." She blinked hard, trying to focus. "Ambient artron energy has an enhancing effect on human immune systems," she explained idly, as she waved the sonic around Yaz's head. "The exposure in a normal year of travel in the TARDIS is very similar to a year of typical background ionizing radiation on Earth. Makes you all healthier, more resistant to alien pathogens and things."

Yaz shrugged. "Okay."

The Doctor stopped scanning, and took a deep breath. "You've just been exposed to about a thousand times that amount."

Yaz flexed her fingers across her thighs, trying to stay calm. "What does that mean?"

"That depends. How do you feel?"

"I feel fine. Better than fine."

"Right. My preliminary scans indicate that your cells have effectively stopped aging."

"Stopped aging." Yaz blinked. "Will they start again?"

"Possibly. But even if they do, the effect is likely to be permanent. Barring any kind of accident, you will probably live for a _very_ long time. And in excellent health."

Yaz nodded, digesting that information. "Oh. Wow. Cool, I guess?" Her face darkened in alarm. "I'm not going to make you sick, am I?"

"No, no," the Doctor said. "The filtering systems insulated you from incompatible particles." 

"Good," Yaz breathed in relief. She sort of stared into a vague middle distance, pondering this new development. She didn't _feel_ different...

The Doctor hung her head. "I'm sorry, Yaz."

"For what?"

"Humans aren't really made to be near-immortal. This might not be what you want. I can probably fix it."

"Fix... not aging."

The Doctor made a face, and shrugged. "You know, _without_ killing you. Except in the long run, I suppose."

Yaz looked at her blankly.

All at once, tumblers clicked for the Doctor and she did some processing of her own. Her face fell, slowly, as realization dawned. "Ohhhhh."

_What's your name?_

_PC Khan, Hallamshire Police._

_Name, not title._

"Doctor?"

She smacked herself in the forehead. "The _title_. Of _course_ , how did I miss that?"

"You're doing it again," Yaz snapped. "Could you please complete an actual thought out loud?"

"Right. Yaz, there's something you should know. Two somethings. Maybe three, depending on the previous two..."

"Doctor!"

"Right, okay. Remember the message in the lab? The first thing is that the word 'child' on Gallifrey was sometimes slang. For 'human.' We weren't very polite about humans, really. Quite disrespectful. A lot of us just didn't know how brilliant you lot can be. It's not my proudest recollection. Anyway."

She paused, gauging the impact of that disclosure, which was next to nothing at all. "The second is the word 'vanquish.' Probably a mistranslation. Maybe just a cheeky overstatement. More like 'subdue' or 'calm,' given context."

Yaz waited, blinking, and had opened her mouth to ask about the "third" thing, when it hit her. She recalled her own translation of the Gallifreyan text. _Unending_...

" _I'm_ the Timeless Child?" she blurted.

The Doctor winced. "Might just be, yeah."

"The message is about _us_?"

The Doctor nodded.

Then she waited. For quite a long time, as Yaz sorted all the implications at once. "Okay, but I'm not going to 'vanquish' you," Yaz finally said, with a doubtful look.

"I believe that," the Doctor assured her. "But context is important."

"Context?" Yaz said, with a faint laugh. "We're millions of light years from Earth, two thousand years after I was born, on a moon with an abandoned lab and some Gallifreyan graffiti that implies I might live forever, and also that I will 'vanquish' the Oncoming Storm, who happens to be _you_?"

The Doctor scrunched her face in growing concern as the litany wore on, unsure of how to read Yaz's tone. "More like 'calm,'" she corrected. "This is kind of a lot to process, innit? Seems like a lot." She spun around and groaned in frustration. "Ah, Yaz. I'm _so_ sorry. I didn't know this would happen."

Yaz sat, a little dazed. She couldn't really argue; it really was a lot of information to take in.

"I can take you home. Or literally anywhere," the Doctor rambled, desperate to offer something that could somehow fix this massive change. "What would help? What do you want?"

"I want more," Yaz murmured.

The Doctor paused her anguished flapping. "Sorry?"

"More of the universe. More time with you," Yaz continued, quoting herself from what felt like a very long time ago. Her face transformed in a slow, joyful grin. "I think I just got my wish."

She pushed herself off the exam table and sauntered out of the medbay, leaving a speechless Doctor behind.

* * *

_You lead but you're scared, too, for yourself and for others. Afraid of your own newness. We see deeper, though, further back..._

_We see what's hidden, even from yourself._

In the middle of what passed for night, the Doctor wandered around the TARDIS console with listless disinterest, flipping a lever here and there, quite lost in her own thoughts.

She'd long since grown used to living out of order, to uncovering herself at the whim of a capricious and tangled universe.

This was a little different. While she could live with such uncertainty on her own behalf, she worried for Yaz, who was now firmly enmeshed in a complicated destiny that was both already written and yet to be revealed.

She leaned against the console and sighed. "Guess you knew this was going to happen," she muttered to the TARDIS. "That's why you've looked after her."

"She did a good job," Yaz murmured as she wandered up, carrying the Doctor's journal. "Made this place a home."

The Doctor straightened, and spent a moment wiping imaginary dust from an indicator on the console. "Oh. Hi."

"Hi," Yaz said, with a shy smile. "I brought back your journal. I couldn't find the bit you wrote about me, though."

The Doctor relieved her of the book and flipped to the mostly blank pages in the back, then pointed out the relevant glyphs. "We never got to that part of the Gallifreyan lesson," she murmured.

Yaz traced the text with a careful fingertip. "What does it say?"

"It says, 'She'll change everything.'"

Yaz cast a skeptical look back at her. "Except that's not the right tense," she accused, mildly.

"You're right," the Doctor admitted. "'She already _has_ changed everything.' And she will. And she does." She made a face that scrunched in embarrassment. "I wrote that after that bit with the spiders. I already knew you were special."

"Aw," Yaz said, with a grin. She bumped against the Doctor in a gentle tease.

The Doctor frowned, as if concentrating on the brief touch. After a moment she swallowed, rocked forward on her feet, then retreated again. "You know, we've been together a while now, at least in our shared subjective experience of linear time. And, I know... I _think_ I know that you fancy me, at least a little."

 _A little?_ Yaz blinked in surprise, but the Doctor was already rambling onward before she could interrupt.

"Over all the lifetimes, I've tried just about everything once, so far as falling in love, or trying my very hardest _not_ to fall in love, or getting married and loving all out of order. A lot of that was brilliant, in its way. But thought I might try something different this time around."

"What's that?" Yaz felt her heartbeat trip, then pound heavily in her ears, threatening to drown the Doctor out entirely.

"I thought I might just ask if you'd be keen to kiss me, then take it from there?"

Yaz froze, and had to take a moment to remember to breathe. She took the journal out of the Doctor's hands, carefully closed it, set it aside on the console, then waited for the Doctor to look back at her. "Really?" she asked.

"Which part?" the Doctor replied, confused. "Although now I realize, after the fact, that I might have been ambiguous, just then. I quite fancy _you_. Sorry if I skipped that part. I honestly can't remember ever being this nervous."

Yaz melted a bit, and gave her an encouraging smile. "Hey, nothing to be nervous about," she said. "It's just me."

"'Just' you," the Doctor repeated, laughing at herself. " _Just_ brilliant, amazing Yaz, who changes everything." She took hold of one of Yaz's hands, and immediately felt steadier. "You asked me to think about it," she continued. "So I did. And all I could think about was how lovely it is to know you're around, and not just when I was sick, and not just when I thought you might be gone. The thing is, I don't want you to feel obligated just because the universe is being pushy."

"Definitely not feeling obligated," Yaz said. "More like... validated? I _knew_ we were proper special. And now the universe agrees with me." She gave the Doctor a slightly smug look, and squeezed her hand. "So what if I _were_ keen to kiss you?"

The Doctor's eyes flicked to Yaz's lips, suddenly so close, and she faltered. Her shyness left Yaz emboldened, more confident now that feelings were exposed to open air. 

Yaz shifted closer, feeling the warmth in the scant space between them. She lifted her free hand to the Doctor's waist, sliding under the long coat, across the soft, skin-warmed surface of the shirt worn below. She bent her head and leaned in so that they were nearly cheek to cheek, and could hear the sound of the Doctor's quickened breathing against her ear.

"Yaz," the Doctor whispered, and they turned into each other, brushing their lips together once, then again. 

The Doctor uttered the faintest breathless groan, which made Yaz grin before she closed in and kissed her in earnest. Their hands untangled in favor of holding each other closer, stoking the sweet contact.

Yaz broke away to catch her breath, and could feel the Doctor's radiant smile as they tilted their foreheads together. "If you make a 'snogging with Yaz' joke, I'm leaving," she warned.

The Doctor made an indignant noise. "Excuse you. I am hardly that predictable."

Yaz laughed, then leaned back in to meet the Doctor's grin with her own.

They stayed together that way through the night, trading kisses and shy smiles, savoring the rare quiet of a universe at peace.

Unnoticed, the TARDIS took the opportunity to drop out of time, letting her thief and her thief's human have the moment they deserved.

**Author's Note:**

> The series will continue. :)
> 
> Many, many thanks for all the kind comments and kudos. I appreciate them more than I can express.
> 
> And thank you for (still) reading!


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